Heat pipe

ABSTRACT

A heat pipe ( 10 ) includes a metal casing ( 12 ) having a closed end ( 14 ) and a sealed end ( 16 ) located opposite to the closed end. The sealed end of the heat pipe includes a cramped section ( 16   a ) having a wave-shaped cross-section. A device for sealing an open end ( 16   a ) of the heat pipe includes a pair of clamping blocks ( 26 ) for clamping the open end of the heat pipe in a first direction and a pair of pressing blocks ( 22, 24 ) located at opposite sides of the open end of the heat pipe and being capable of moving towards each other, thereby approaching the open end of the heat pipe in a second direction perpendicular to the first direction. The pressing blocks have a pair of complementary wave-shaped forming faces ( 22   a,    24   a ) formed thereon.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus for transfer ordissipation of heat from heat-generating components, and moreparticularly to a heat pipe.

DESCRIPTION OF RELATED ART

It is well known that heat is generated by a variety of electroniccomponents such as central processing units (CPUs) of computers duringtheir normal operations. Since the workability and stability of theseelectronic components depend, to a large extent, on timely removal ofthe heat generated by them, cooling devices such as heat sinks pluscooling fans are commonly used in order to remove the generated heataway. Currently, heat pipes are widely used in combination with thecooling devices so as to timely and effectively remove the heat fromthese electronic components.

Heat pipes are an effective heat transfer means due to the applicationof the phase-change mechanism. A heat pipe is usually a vacuum casingcontaining therein a working fluid. In most cases, a wick structure isprovided inside the heat pipe, lining an inner wall of the casing. Inoperation, a cooling device such as a plurality of metal fins isattached to a condensing section of the heat pipe and an evaporatingsection of the heat pipe is maintained in thermal contact with aheat-generating component. The working fluid contained in theevaporating section of the heat pipe absorbs heat generated by theheat-generating component and evaporates into vapor which thereaftermoves towards the condensing section of the heat pipe where the heatcarried by the vapor is released to ambient environment via the metalfins thermally contacting the condensing section. As a result, the vaporis condensed into condensate in the condensing section and then thecondensate is drawn, via the wick structure arranged in the heat pipe,back to the evaporating section for being available again forevaporation.

Generally, a heat pipe is made by filling a working fluid into a tubewith an open end and a closed end. In the tube, a wick structure isdisposed. Then, the tube is vacuumed via the open end and the open endof the tube is sealed. Among these steps, the sealing step is extremelyimportant because a defective sealing will directly affect theperformance and life span of the heat pipe.

Currently, a technique of sealing the heat pipe involves filling a tinblock or epoxy material into the open end of the heat pipe. However, byusing this technique, a complicated process is generally required, whichadds manufacturing cost to the heat pipe. Also, if the heat pipe made bythis technique is thereafter bent or flattened in order to be applicablein some specific situations where the heat pipe is desired to be in acurved or flattened configuration, the sealed open end of the heat pipewill deform and a small gap will accordingly occur at the sealinginterface between the sealed open end of the heat pipe and the fillingmaterial. Due to the gap, the heat pipe will gradually lose its vacuumcondition and a reliability issue will be raised. As a result, theapplication of the heat pipe made by this technique is somewhat limited.

Mechanical pressing is another technique applicable for sealing the heatpipe. In this technique, a device is used to flatten a section of theopen end of the heat pipe into a flattened sealing section and then, adistal end portion of the open end is soldered so as to hermeticallyseal the heat pipe. In this case, the distal end portion is formed as aball. Since the flattened sealing section is thin and flat, it generallyhas a low mechanical strength and is therefore easily deformed whensubject to external forces or high temperatures. For example, if theheat pipe made by this technique is vertically soldered to a heat sinkunder a high temperature, the flattened sealing section of the heat pipewill soften and deform due to a weight of the ball-like distal endportion, as shown in FIG. 6.

Therefore, it is desirable to provide a heat pipe which overcomes theforegoing disadvantages.

SUMMARY OF INVENTION

The present invention relates, in one aspect, to a heat pipe. The heatpipe includes a metal casing having a closed end and a sealed endlocated opposite to the closed end. The sealed end of the heat pipeincludes a cramped section having a wave-shaped cross-section.

The present invention relates, in another aspect, to a device forsealing an open end of a heat pipe. The device includes a pair ofclamping blocks for clamping the open end of the heat pipe in a firstdirection and a pair of pressing blocks located at opposite sides of theopen end of the heat pipe and being capable of moving towards eachother, thereby approaching the open end of the heat pipe in a seconddirection perpendicular to the first direction. The pressing blocks havea pair of complementary wave-shaped forming faces formed thereon. Thepressing blocks presses the open end of the heat pipe into the crampedsection of the sealed end of the heat pipe.

Other advantages and novel features of the present invention will becomemore apparent from the following detailed description of preferredembodiment when taken in conjunction with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an isometric view of a heat pipe in accordance with oneembodiment of the present invention;

FIGS. 2-5 are cross-sectional views of a device used in manufacturingthe heat pipe of FIG. 1 at different steps; and

FIG. 6 is a side elevation view of a heat pipe in accordance with theconventional art.

DETAILED DESCRIPTION

FIG. 1 illustrates a heat pipe 10 in accordance with one embodiment ofthe present invention. The heat pipe 10 includes a metal casing 12having an integrally closed end 14 and a sealed end 16 located oppositeto the closed end 14. The sealed end 16 includes a distal crampedsection 16 a and a transitional tapered section 16 b located between themetal casing 12 and the cramped section 16 a. The cramped section 16 ais centrally aligned with a longitudinal axis of the metal casing 12.The cramped section 16 a has a wave-shaped cross-section, which issymmetric with respect to the longitudinal axis of the metal casing 12.In this figure, the cramped section 16 a has an S-shaped cross-section.

Generally, the cramped section 16 a is formed by mechanically pressingan original open end 16 a′ of the metal casing 12 through a device,whereby the heat pipe 10 is sealed. With reference also to FIGS. 2-5,such a device is shown for forming the cramped section 16 a andaccordingly sealing the heat pipe 10. The device includes a pair ofclamping blocks 26 and a pair of pressing blocks 22, 24. The clampingblocks 26 are used to clamp the open end 16 a′ of the metal casing 12 ina first, horizontal direction, as viewed from FIG. 2. The pressingblocks 22, 24 are located at opposite sides of the open end 16 a′ andare capable of moving towards each other in a second, vertical directionperpendicular to the first, horizontal direction, as viewed from FIG. 2.The pressing blocks 22, 24 have a pair of complementary S-shaped formingfaces 22 a, 24 a formed thereon, respectively, which are used to formthe S-shaped cramped section 16 a of the heat pipe 10.

In operation, the open end 16 a′ of the metal casing 12 is sandwichedbetween the two clamping blocks 26, as shown in FIG. 2. Then, thepressing blocks 22, 24 are brought to move towards each other, therebyapproaching the open end 16 a′ in a high speed. As a result, the openend 16 a′ is pressed by the pressing blocks 22, 24 into the S-shapedcramped section 16 a′, as shown in FIG. 3. During the movement towardthe open end 16 a′, the pressing blocks 22, 24 are guided between theclamping blocks 26, which are spaced from each other by a distancesubstantially the same as a diameter of the open end 16 a′ of the casing12. Thereafter, a cutter 32 is used to cut away a distal end portion ofthe cramped section 16 a formed by the above-mentioned mechanicalpressing step in order to obtain the cramped section 16 a with adesirable length and a straight edge, as shown in FIG. 4. Finally, thepressing blocks 22, 24 are removed away from the formed cramped section16 a, as shown in FIG. 5. In order to ensure that the heat pipe 10sealed by this device is hermetically sealed, a subsequent solderingprocess may be applied to the formed cramped section 16 a. By using thepresent device, the sealing process to the heat pipe 10 can be performedin a very short time period, typically with a cycle time of about 5seconds.

In the present heat pipe 10, the wave-shaped cramped section 16 a of thesealed end 16 has a relatively high mechanical strength. Thus, the heatpipe 10 is hermetically sealed and has a good mechanical performance.When the heat pipe 10 is soldered to a heat sink under a hightemperature, the sealed end 16 thereof will not deform. In use, aportion of the heat pipe 10 neighboring the closed end 14 is used as anevaporating portion for receiving heat from a heat generating electronicdevice, such as a CPU, and a portion neighboring the sealed end 16 isused as a condensing portion for dissipating the heat.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size, and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. A heat pipe comprising a metal casing having an integrally closed endand a sealed end located opposite to the closed end, the sealed endincluding a cramped section having a wave-shaped cross-section.
 2. Theheat pipe of claim 1, wherein the cramped section has an S-shapedcross-section.
 3. The heat pipe of claim 1, wherein the cramped sectionis symmetric with respect to a longitudinal axis of the metal casing. 4.The heat pipe of claim 1, wherein the cramped section is centrallyaligned with a longitudinal axis of the metal casing.
 5. The heat pipeof claim 1, wherein the sealed end further includes a tapered section,the tapered section being located between the metal casing and thecramped section.
 6. A device for sealing an open end of a heat pipecomprising: a pair of clamping blocks for clamping the open end of theheat pipe in a first direction; and a pair of pressing blocks located atopposite sides of the open end of the heat pipe and being capable ofmoving towards each other, thereby approaching the open end of the heatpipe in a second direction perpendicular to the first direction, thepressing blocks having a pair of complementary wave-shaped forming facesformed thereon.
 7. The device of claim 6, wherein each of thecomplementary wave-shaped forming faces has an S-shaped configuration.8. A heat pipe comprising: a casing having an integrally closed end nearan evaporating portion of the heat pipe and a cramped sealed end near acondensing portion of the heat pipe, wherein the cramped sealed end hasa wave-like cross section.
 9. The heat pipe of claim 8, wherein thewave-like cross section has an S-shaped configuration.
 10. The heat pipeof claim 9, wherein the S-shaped sealed end is centrally aligned with alongitudinal axis of the casing.
 11. The heat pipe of claim 10 furthercomprising a tapered section adjacent to the cramped sealed end.